1. Field of the Invention
The present invention relates to an optical device, an optical system a method of production of the optical device, and a mold for production of the optical device.
2. Description of the Related Art
When producing a lens, the following first to third methods of production have been known.
The first method of production is a method of filling an optical material such as molten glass in a metallic mold formed with a cavity of a desired lens shape machined to an intended lens shape to produce a mold lens.
The second method of production is a method of utilizing reactive ion etching (RIE) or other etching and using a photo resist or the like as a mask (etching mask) to etch an optical material to a predetermined shape to thereby produce a lens made of the related optical material.
The third method of production is a method of mechanically polishing a base made of an optical material to the lens shape to produce the lens.
In the conventional first method of production, that is, the method using simple molding, it is difficult to produce a small sized lens having a large numerical aperture (NA), so it is difficult to reduce the lens diameter to 1 mm or less.
In the conventional second method of production, that is, the method using RIE or other etching, there is a problem in that there are restrictions on the optical material and there are a few optical materials of high refractive indexes capable of obtaining lenses having large numerical apertures among the optical materials capable of RIE and other etching, so it is difficult to use a material having a high refractive index and it is difficult to realize a lens having a large numerical aperture NA.
In the conventional third method of production, it is difficult to manufacture a small sized lens.
If increasing the numerical aperture of the lens, it is possible to make the size of a light spot created after passing through the lens small. It is desirable from the viewpoint of increase of the capacity of an optical disc to enlarge the numerical aperture NA of the lens (object lens) of an optical head.
Also, lenses and other optical devices are being used for various optical apparatuses. Reduction of the size of the optical devices is desirable from the viewpoint of the reduction of size of the optical apparatuses such as an optical disc apparatus and an optical pickup.
In order to realize an optical device having a large numerical aperture, a large refractive index of the optical material is effective.
As an optical material having a high refractive index in a region of visible light, there are titanium oxide, tantalum oxide, gallium phosphate (gallium phosphorus), gallium nitride, silicon nitride, etc.
However, it is difficult to machine these materials to small sized lenses having a large numerical aperture in the prior art.
Also, many conventional lenses have irregular shapes. In order to align a plurality of lenses of such irregular shapes, high precision positioning in three-dimensional directions is necessary, so the load of the alignment work is large.
Also, when comprising a flying head (floating head) consisting of an optical head mounted on a swing arm, the optical head can be prepared by separately preparing a slider and the lens and attaching them at a high precision, but in this case, the load of the attachment work and accordingly the load of preparation of the optical head is large.
An object of the present invention is to provide an optical device having a small size, or a small size and a large numerical aperture.
Another object of the present invention is to provide an optical system comprising the optical device, that is the optical device having a small size, or a small size and a large numerical aperture. Still another object of the present invention is to provide a method of production of an optical device for producing such optical device, that is the optical device having a small size, or a small size and a large numerical aperture.
Further, still another object of the present invention is to provide a mold for production of an optical device for using in such method of the optical device.
According to a first aspect of the present invention, there is provided an optical device comprising a first optical portion made of a first optical material and having a concavity; and a second optical portion comprising a second optical material having a refractive index different from that of the first optical material, and inserted into the concavity.
According to a second aspect of the present invention, there is provided a method of production of an optical device comprising a first optical portion made of a first optical material and having a concavity and a second optical portion comprising a second optical material having a refractive index different from that of the first optical material, and inserted into the concavity, including: a step of injecting the first optical material into a metallic mold formed with a projection projecting out into a cavity to form the first optical portion made of the first optical material with a concavity reproducing the shape of the projection; and a step of filling the second optical portion in the concavity of the molded.
According to a third aspect of the present invention, there is provided a method of production of an optical device comprising a first optical portion made of a first optical material and having a concavity and a second optical portion comprising a second optical material having a refractive index different from that of the first optical material, and inserted into the concavity, including: a step of forming a resist having a hole in the flat surface of the first optical portion made of the first optical material; a step of forming a concavity corresponding to the hole in the first optical portion by etching; a step of removing a resist from the first optical portion with the concavity formed therein; and a step of filling the second optical portion in the concavity of the first optical portion from which the resist is removed.
According to a fourth aspect of the present invention, there is provided a method of production of an optical device comprising a first optical portion made of a first optical material and having a concavity and a second optical portion comprising a second optical material having a refractive index different from that of the first optical material, and inserted into the concavity, including: a step of forming on a third optical portion provided with a projection and having a flat area around the projection the first optical portion made of a layer of the first optical material burying the projection, a step of flattening the surface of the first optical portion to form a flat surface and bonding the related flat surface to a third base material made of a third optical material, a step of removing the third optical portion from the first optical portion bonded to the third base material to expose the concavity reproducing the shape of the projection in the first optical portion, and a step of filling the second optical portion in the concavity of the exposed first optical portion.
According to a fifth aspect of the present invention, there is provided a method for production of an optical device wherein a second optical portion having a refractive index different from a first optical material is filled in a concavity of a first optical portion made of the first optical material, comprising: a step of forming resist films having windows on substantially flat first and second flat surfaces facing each other of a first optical portion made of the first optical material; a step of forming concavities corresponding to the windows in the first and second flat surfaces of the first optical portion by etching; a step of removing the resist films from the first optical portion with the concavities formed therein; and a step of filling the second optical portion in the concavities of the first and second flat surfaces of the first optical portion from which the resist films have been removed.
According to a sixth aspect of the present invention, there is provided a method for production of an optical device wherein a second optical portion having a refractive index different from a first optical material is filled in a concavity of a first optical portion made of the first optical material, comprising: a step of forming on a third optical portion provided with a first projection and having a flat area around the first projection a first optical portion made of a layer of the first optical material burying the first projection; a step of forming on a fourth optical portion provided with a second projection and having a flat area around the second projection a third optical portion made of a layer of the first optical material burying the second projection; a step of flattening the surface of the first optical portion to form a flat surface and bonding the related flat surface to a first flat surface among facing first and second flat surfaces of a fifth optical portion made of a third optical material; a step of flattening the surface of the third optical portion to form a flat surface and bonding the related flat surface to the second flat surface of the fifth optical portion; a step of removing the second and fourth optical portions from the first and third optical portions bonded to the fifth optical portion and exposing concavities with the shapes of the first and second projections transferred thereto in the first and third optical portions; and a step of filling the second optical portion in the concavities of the exposed first and third optical portions.
According to a seventh aspect of the present invention, there is provided an optical device, comprising: a convex lens formed with a convex curved face; and a first optical portion closely contacting the convex curved face of the convex lens, wherein; the first optical portion has first and second faces facing each other, a concave curved face closely contacting the convex curved face being formed in the first face, and a hole communicating with the second face being formed from a deep side of the concave curved face, and part of the convex curved face of the convex lens is exposed in the hole of the first optical portion.
According to a eighth aspect of the present invention, there is provided an optical system comprising first and second optical devices, wherein; the first optical device has a first convex lens formed with a convex curved face and a first optical portion with the convex curved face of the first convex lens bonded thereto; the first optical portion has first and second faces facing each other, a concave curved face closely contacting the convex curved face being formed in the first face, and a hole communicating with the second face being formed from a deep side of the concave curved face; part of the convex curved face of the first convex lens is exposed in the first hole of the first optical portion; the second optical device has a second convex lens with the convex curved face formed thereon and a third optical portion with the convex curved face of the second convex lens bonded thereto; and the third optical portion has third and fourth faces facing each other, a concave curved face closely contacting the convex curved face of the second convex lens being formed in the third face, and the first and second optical devices being bonded so that the optical axes of the first and second convex lenses coincide or substantially coincide.
According to a ninth aspect of the present invention, there is provided a method for production of an optical device having a convex lens and a first optical portion closely contacting the convex curved face of this convex lens, comprising: a step of using a metallic mold formed with a projection projecting out into a cavity to mold a first optical portion formed with a concavity reproducing the shape of the projection; a step of filling an optical material in the concavity of the molded optical portion; a step of flattening the surface of the optical material filled in the concavity to form the convex lens; and a step of forming a hole so that part of the convex curved face closely contacting the concavity in the convex lens is exposed in the first optical portion.
According to a tenth aspect of the present invention, there is provided a method for production of an optical device having a convex lens and a first optical portion closely contacting the convex curved face of this convex lens, comprising: a step of forming a first resist film having a first window in the flat surface of the first optical portion; a step of forming a concavity corresponding to the first window in the first optical portion by etching; a step of removing the first resist film from the first optical portion formed with the concavity; a step of filling an optical material in the concavity of the first optical portion from which the first resist film is removed; a step of flattening the surface of the optical material filled in the concavity to form the convex lens; and a step of forming a hole whereby part of the convex curved face closely contacting the concavity in the convex lens is exposed in the first optical portion.
According to a eleventh aspect of the present invention, there is provided a method for production of an optical device having a convex lens and a first optical portion closely contacting the convex curved face of this convex lens, comprising: a step of forming on a third optical portion provided with a projection and having a flat area around the projection a first optical portion made of a layer burying the projection; a step of flattening the surface of the first optical portion to form a flat surface and bonding the related flat surface to a third optical portion; a step of removing the third optical portion from the first optical portion bonded to the third optical portion to expose the concavity with the shape of the projection transferred thereto in the first optical portion; a step of filling an optical material in the exposed concavity of the first optical portion; a step of flattening the surface of the optical material filled in the concavity to form the convex lens; and a step of forming holes whereby part of the convex curved face closely contacting the concavity in the convex lens is exposed in the first and third optical portions.
According to a twelfth aspect of the present invention, there is provided an optical device obtained by forming a concavity by a pin in optical material in a molten state or softened state, hardening the optical material with the related concavity formed therein, and polishing or grinding a face where the concavity is formed so that a hole of a front end of the concavity remains in a first optical portion obtained thereby.
According to a thirteenth aspect of the present invention, there is provided a metallic mold for production of an optical device made of an optical material, comprising a cavity into which an optical material in a molten state or softened state is filled and a pin for forming a concavity in the optical material in the molten state or softened state in the cavity, wherein the pin projects out into the cavity while penetrating through a wall of the cavity from the outside.
According to a fourteenth aspect of the present invention, there is provided a metallic mold for production of an optical device as set forth in claim 119, wherein the hole of the front end of the concavity has a spherical or substantially spherical shape.
According to a fifteenth aspect of the present invention, there is provided a method for producing an optical device by using a metallic mold having a cavity into which an optical material in a molten state or softened state is to be filled and a pin for forming a concavity in the optical material in the molten state or softened state in the cavity, wherein the pin penetrates through the wall of the cavity from the outside and projects out into the cavity, comprising: a step of filling the optical material in the molten state or softened state in the cavity to create a first optical portion formed with the concavity by a simple molding; and a step of polishing or grinding the face of the first optical portion where the concavity is formed so that a hole of a front end of the concavity remains.
According to a sixteenth aspect of the present invention, there is provided a method for producing an optical device by using a metallic mold having a cavity into which an optical material in a molten state or softened state is to be filled and a pin for forming a concavity in the optical material in the molten state or softened state in the cavity, wherein the pin penetrates through the wall of the cavity from the outside and projects out into the cavity, comprising: a step of filling the optical material in the molten state or softened state in the cavity to create a first optical portion formed with the concavity by simple molding; a step of filling an optical material having a refractive index different from that of the first optical portion in the concavity of the first optical portion; and a step of flattening the surface of the optical material filled in the concavity to form a convex lens made of the related optical material.
According to a seventeenth aspect of the present invention, there is provided A method of production of an optical device, comprising: a step of forming a concavity by a pin in an optical material in a molten state or softened state and a step of polishing or grinding the face where the concavity is formed so that a hole of a front end of the concavity remains in a first optical portion obtained by hardening the optical material formed with the related concavity.